You'll Blast More Fat

Forget that "fat-burning" zone on the treadmill. According to a new study published in Obesity, strength training is better at helping people lose belly fat compared with cardio. While aerobic exercise burns both fat and muscle, weight lifting burns almost exclusively fat.

You'll Be Stronger Mentally

"Strength has a funny way of bleeding into all areas of your life, in the gym and out," says Jen Sinkler, an Olympic lifting coach, kettlebell instructor, and author of Lift Weights Faster. By constantly challenging yourself to do things you never thought possible, your confidence grows. "Weight lifting empowers you," she says.

You'll Boost Your Flexibility

Ignore that super ripped guy fumbling in yoga class for just a minute. Researchers from the University of North Dakota pitted static stretches against strength-training exercises and found that full-range resistance training workouts can improve flexibility just as well as your typical static stretching regimen. The key word here is "full-range," notes Sinkler. If you can't complete the full motion—going all the way up and all the way down—with a given weight, you may need to use a lighter dumbbell and work up to it.

You'll Strengthen Your Bones

Weight lifting doesn't only train your muscles; it trains your bones. When you perform a curl, for example, your muscles tug on your arm's bones. The cells within those bones react by creating new bone cells, Perkins says. Your bones become stronger and more dense.

You'll Drop a Size

Strength training has a reputation of making women "bulk up." But it's not true. The more your weight comes from muscle, rather than fat, the smaller you'll be. "In fact, body weight often goes up with strength training, but dress size goes down one or two sizes," Perkins says. Plus, it's really, really difficult to get body-builder huge. "Women produce about 5 to 10 percent the amount of testosterone men do, limiting our muscle-building potential when compared to men," Sinkler says. To seriously gain size, you'd pretty much need to live in the weight room.

You'll Be a Better Runner

Stronger muscles mean better performance—period. Your core will be better able to support your body's weight and maintain ideal form during other exercises (like running), plus your arms and legs will be more powerful. What's more, since strength training increases the number and size of calorie-torching muscle fibers fueling your performance, strength training could actually help you burn more calories during your cardio workouts, Perkins says.

You'll Have a Healthier Heart

Cardiovascular exercise isn't the only exercise that's, well, cardiovascular. In fact, strength training can up your heart health, too. In one Appalachian State University study, people who performed 45 minutes of moderate-intensity resistance exercise lowered their blood pressure by 20 percent. That's as good as—if not better than—the benefits associated with most blood pressure pills.